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Modern Push Processing


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#1 Doug Frerichs

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Posted 16 July 2011 - 02:09 PM

I understand push processing and how it works, but ever since a friend of mine that was about to shoot a student short mentioned that he thought of "pushing a stop in post," I've wondered if pushing is still done chemically or if it is processed normally and then the imaged raised digitally after. I assume it is still done chemically, but part of me is curious.
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#2 Chris Millar

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Posted 16 July 2011 - 05:42 PM

Avoiding a potentially big and freewheeling digital vs. film conversation I'll just say what I know is true:

It can still be done and is regularly done chemically

'pushing in post' is a bit of a misnomer - but I think I know what they mean ...

Let the forum fun begin ....

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#3 Doug Frerichs

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Posted 16 July 2011 - 06:48 PM

Would you say that bigger budget films would be the ones that most commonly still do it chemically? Like I just read in the AC article about "Super 8" that the night footage was pushed a stop, so do you think those were most likely done chemically since it was a big budget film?
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#4 Chris Millar

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Posted 16 July 2011 - 06:57 PM

Of the big budget films I've worked on I've been no where near the people that make those sorts of decisions, so cant say with any authority - but I'd say certainly yes, it's talked about a lot online at least ...

From my own 16mm push processing I think it was only about %6 more cost per foot in processing, maybe that'll give you a clearer idea of the cost 'barrier' (if you could call it that) - there are other small technical barriers, mostly in understanding, but once you know what you're doing they disappear...
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#5 Charles MacDonald

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Posted 16 July 2011 - 08:39 PM

he thought of "pushing a stop in post," I've wondered if pushing is still done chemically or if it is processed normally and then the imaged raised digitally after.


Both methods will give slightly different effects. You can't really "push" in post but you can adjust the exposure of the print. Digitally you can distort the rendition all you like.

if you KNOW that you need to push the negative, it is worth considering doing a push when the film is being developed, as you have a chance to pick up more shadow detail at the developing stage, once the Negative is processed, you are stuck with what is on the film.
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#6 K Borowski

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Posted 17 July 2011 - 06:55 PM

I'd say about 100% of the time in the "pros" it's done chemically (actually an increase in developer TIME not special chemicals).


Ultimately, though it is a bit of a holdout from the pre-DI days. What a push does is increase contrast and highlight speed (NOT shadow speed, therefore increase in contrast is casused by detail lost in the shadows) Without a push, straight optical or contact printing, you could correct it back but your image started to get milky and flat. A push would add contrast (and then some) that would give it more of a normal look, although you'd have pitch-black shadows and an increase in grain.

Digitally, you can tweak the contrast easily, but you'll get digital noise instead of grain if you overdo it. You'd have to test one against the other. For a simple one-stop push I'd definitely just do it at the lab.

Only in an extreme situation maybe with a push two, would I contemplate not doing things traditionally. Cinematographers used to underexpose 100ASA neg. back in the '70s when that's all there was, two stops, push one and pirnt up the other one so as not to get too much grain and contrast.

I'd contemplate doing something similar with a two stop underexposure, one stop push and correcting the rest digitally.




Problem is, a bad telecine or scan session, if they don't adjust the ANALOG gain on the scanner to scan the shadows at the correct intensity you can run into a tun of, in my opinion far more objectionable digital noise.






One further disadvantage that David Mullen often mentioned on here with both skip bleach and pushing is that the 2ndary solutions get their times extended as well, harming image longevity.

I can tell you the machine I run film on is guilty of this. We can speed the film up again immediately after it has cleared developer, but often times we aren't there right when it clears. Over-bleaching film probably doesn't aid image permanence of the dyes any, and probably increases reddish stain (shows up cyan) on the negative.




And, with pushing, you get to a point where the true film speed increase goes to zero and you start to get highlight speed increases at the expense of image quality on what IS developed in the shadows, your base fog goes WAY up past a certain point and you get some ugly milky grainy shadows.



With a good scanner and scanner operator,in the DI world, a one stop push is almost unnecessary, as you're not even getting a full stop of detail bak in terms of the speed increase. But there are plenty of bad habits, lazy operators who "know better" than the instructions sometimes. You'd be surprised how reluctant some labs are to turn up the intensity of the scan head to see into severe overexposure. With pushing, if not properly adjusted, you can gain grain and get jet-black shadows and have the scanner intensity not increased to punch through the denser highlights, getting blowouts.
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#7 Daniel Lee

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Posted 18 July 2011 - 02:17 AM

A two stop push on ECN-2 according to Kodak (with their film) gives a 2/3rd's of a stop increase in film speed;

ie: There is 2/3rds of a stop of shadow detail on the toe not developed in normal procssing.


Normal exposure + a small push also has it's uses.
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#8 Daniel Lee

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Posted 18 July 2011 - 02:30 AM

A two stop push on ECN-2 according to Kodak (with their film) gives a 2/3rd's of a stop increase in film speed;

ie: There is 2/3rds of a stop of shadow detail on the toe not developed in normal procssing.


Normal exposure + a small push also has it's uses.



On top of that there is plenty of latitude below exposure;

ie: There is 4 stops below exposure in a straight line -before- hitting the toe (at least for 5201 50D) with normal processing. So if you exposure is X, and you spot meter something, if X is 4 stops 'underexposed' from that reading than that spot metered area will show up on the straight line before the toe in the shadow portion.

There is an extra 2 stops on the toe.

So in this example if there was a minimum detail in the shadows you wanted to record, you could spot meter that, and underexpose that by 6 and 2/3rds of a stop with a 2 stop push process (or just 6 stops with N process), though even with accurate metering there'll be 1/3rd of a stop error margin, and you'd not want that minimum detail level right at the cut off point, so a stop inside of that would be wise (5 stops, or 5 and 2/3rds of a stop etc for N+2).

You might find the darkest region is only 3 stops under incident metering, so if you based your exposure on the spot metering of the darkest detail -5 stops (or -4 to keep it off the toe, depending on your end usage), therefore even though there is no lost detail your negative would still be considered thin and less optimal for scanning that exposing for incident, so in that case you could use a +1 or +2 push.



Conversely if your darkest detail you want is 7 stops under incident, you may want to expose as the spot metered shadow -4 stops, or incident +3 stops, and let midtones fall more on the highlight area of the line, the film should retain highlight detail, it's up to you to choose where to clip or how to display that contrast.
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#9 Daniel Lee

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Posted 18 July 2011 - 02:37 AM

Sorry it's not letting me edit..


Now come to a film made for pushing... 5219 500T, still around 4 stops to the toe, and another 4 stops for the actual toe itself.

You could spot meter your darkest part of the scene in reflectivity, and underexpose that by 7 2/3rd to 8 stops to ensure that detail is there with a 2 stop push. Extremely useful for a low contrast range scene thats very low in overall light level.

Kodak page: http://motion.kodak....mation/push.htm
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#10 K Borowski

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Posted 18 July 2011 - 08:53 AM

You're going to get some horrendous grain for those extra 2/3 of a stop, and those are 2/3 of a stop under the already large latitude range.

I'd only push 16mm in an extreme emergency, it's already quite grainy in the '19.



YOu might be able to get something to REGISTER at 8 stops under, but it is not going to be normal enough looking to be USABLE. It's going to be extremely grainy, flat, and milky with extreme underexposure.


With neg. film I like to keep everything within a -1 to +5 stop range that I want to be able to "recover" without it starting to become distorted, grainy.
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#11 John Sprung

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Posted 18 July 2011 - 01:21 PM

One further disadvantage that David Mullen often mentioned on here with both skip bleach and pushing is that the 2ndary solutions get their times extended as well, harming image longevity.



It depends on the machine. On some of them, you could raise the roller assembly out of the tanks -- in the light, not running of course, with leader in the machine -- and re-thread to increase the length of the path in the developer only. That took a while, and pushes were run last, after all the normal jobs. Developing lines are all one-off hand made from standard parts, it's not like buying a Toyota that's exactly like millions of others.

To the original question, pushing should be done chemically. If you don't, you lose part of the latent image, and there's no way to get it back. The lab is part of post, so in that sense, all pushing is in post.



-- J.S.
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#12 K Borowski

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Posted 18 July 2011 - 05:02 PM

While, technically, you are riht John, taht the lab is part of post (just like a DI needs film in film out), most people mean [digital] post.


As far as pushing goes, you can even turn the speed down right as the last of the film leaves the stop bath, but it's more a matter of being undermanned, needing someone to catch it right as this happens (being undermanned, or being apathetic) that prevents this.

Like today, I just ran a push two 15 minutes past our normal shutdown time, and got it out the door at 5. . . I really cheated on the secondaries, but it was print stock, in a non-critical application.



If a push two is only giving you 2/3 stop true speed gain (sounds about right), then a push one has to be giving you less than that, at most 1/2 stop. I'd say in most situations a push one is worth it, even with a grain penality. Push two, honestly, you're gaining mostly contrast (can be added as well, better digitally) and little to no speed.

And again, the d-max is getting up past the point a lot of neg. film scanners are set for (again the operator can adjust for it, but most of the time it never is), so you may be loosing some information at the other end to see that extra sixth of a stop of true speed into the shadows ( 0.03-4 on a densitometer).



Pushing is still designed with optical printing in mind. No one (including myself, I'm making educated guesses here about optimal combinations of developer increase and analog gain adjustment on the scanner), has bothered to actually sit down and examine the effects of one versus the other side by side. (You're right a lot of times digital adjustment is done after-the-fact; that is not what I am talking about though, I'm talking about scanner corrections as the film is goiing through).


Look at 5299 scan film. That is Kodak's second (and probably final) attempt at a digital-optimized film with a super-low gamma, super-wide latitude. People wanted the orange base (needless with digital equipment) instead so they axed it. Looking at the characteristic curve (if I could find some old stock I'd love to test it out myself. . .) it is far more versatile that 5219 in terms of latitude.




I think this is more a case of old habits dying hard. I'd love to hear Rob's opinion on this, or Dominic's. Have been too busy myself to conduct that test of all the films against one another and scanned with different analog gains and exposure modifications. If Kodak keeps discontinuing filmstocks though, it is going to get a lot easier soon! ;-/
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#13 Charles MacDonald

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Posted 18 July 2011 - 07:16 PM

One point is that the Bleach and fix for the most part are "to completion" steps. The bleach runs long enough to get the silver converted to a halogen - and convert the Cyan dye to the finished (Oxidised) state. The Fixer gets all the halide out of the film and the wash removes the fixer and salts. Doing a "Pull" by speeding the machine up may have issues with the baths, but Pushing by slowing the machine down and therefore also over bleaching and over fixing is unlikely to Cause stability problems.
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#14 Daniel Lee

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Posted 18 July 2011 - 07:55 PM

K Borowski, it's not an orange base, it's a mask, the mask is not uniform in density, it is uneven by design, it is there for colour correcton to prevent colour cross-over.

Pushing is used to match densities of underexposure against normal exposure, that's not usually the problem.

The image would only be as described if you're trying to lift those shadows exposed as shadows at the bottom of the range as the darkest detail in your pic with nothing below them into mid tones, which I don't see why someone would attempt that. If you've spot metered your darkest shadow and placed it at -7 you would leave it as a shadow while having everything else rise above it.



The film doesn't have an orange mask because the printing process is matched to that. The printing process is matched to the film because the film has an orange mask, and the film has an orange mask to keep accurate colour.

Edited by Daniel Lee, 18 July 2011 - 07:58 PM.

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#15 K Borowski

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Posted 18 July 2011 - 09:38 PM

One point is that the Bleach and fix for the most part are "to completion" steps. The bleach runs long enough to get the silver converted to a halogen - and convert the Cyan dye to the finished (Oxidised) state. The Fixer gets all the halide out of the film and the wash removes the fixer and salts. Doing a "Pull" by speeding the machine up may have issues with the baths, but Pushing by slowing the machine down and therefore also over bleaching and over fixing is unlikely to Cause stability problems.


@Charles You're right of course. IDK about over-bleaching, over-fixing though, the latter is probably fine for dyes, is bad for B&W. Bleach, just by its rather harsh chemical composition, I wouldn't want to have the film in there double for. Probably lowering the temperature would have a similar effect as lowering time.

I guess someone would need to do some stability tests. Those wack-jobs at Wilhelm imaging don't give a flying f___ about any sort of imaging that isn't done with a mouse and ink cartridges anymore. They're probably wondering why we aren't "all digital!" yet.


@Daniel

Are you arguing semantics with me? Or is there a point you're trying to make I'm not getting?

I'd think it IS uniform in density, as it develops out in B&W, E-6, RA-4 chemistry as well. I measured it once, and the colors were about the same in Dektol as they are in C-41. Not sure about ECN-2, but i'd assume it'd behave similarly. Used still film to avoid the hassle of the rem-jet backing. Something like 0.20 Cyan, 0.65 Magenta, 0.90 Yellow Status M if I recall correctly, so the dyes in the different layers vary by about two and a half stops from one another (at a gamma of 0.6 or so. But the values are constant. I wouldn't think the base would somehow vary with exposure so that it compounds itself, although the colors do shift due to other factors.


In any case, I know what it is there for, OPTICALLY. The sort of color pollution you would get printing a clear-base film like X-processed E-6, could be corrected out quite easily in the digital realm. What I want to know is how it's formed. I know the film itself is clear, it's in the dye layers, so are they fogged selectively?


I'm sorry, but I don't catch the drift of your last sentence. Could you restate please?
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#16 Daniel Lee

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Posted 19 July 2011 - 12:30 AM

The orange mask is not uniform it is inversely proportional to the density of the other layers underneath, ie; the mask as a whole is inversely proportional to the image, if you have no-exposure of course it will be even because there is nothing to mask. Manufacturers do their best to make non-masked film colour accurate (one way to help with that is very high saturation such as E-6, or maskless colour neg) but it is simply not as colour accurate, there is colour crossover. It's not something easily corrected out, nor should you have to.

The film isn't made with an orange mask to match the printing process, the printing process is made to match masked film. Film was made masked because it is far more colour accurate than unmasked film directly on the negative, print materials were then altered to match the advancement in the film. The dyes are simply impure.

Edited by Daniel Lee, 19 July 2011 - 12:34 AM.

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#17 John Sprung

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Posted 19 July 2011 - 05:25 PM

OK,the orange layer thing:

The orange stuff you see on negatives and IP's isn't a separate layer. It's part of the layers that form blue and green. The reason for it is the limitations of real world dyes.

In any imaging system, you want your primaries as saturated as possible, to get the widest possible color gamut. That means that, for instance, you want your green dye to pass a lot of green light, but very little of the red or blue light. It turns out that for complicated chemical reasons, the dyes that exist in the real universe vary across the spectrum, with nice sharp cutoffs available in the reds, but getting less sharp as you go towards the blues. Even the best blue dyes block a lot of blue, and pass a lot of red and green.

So here's the brilliant idea: You can borrow some of the sharpness of the cutoff available in yellow and orange to help out the poor blues and greens.

The red-forming layer gives you red where it's exposed, and clear where it's not. But the green-forming layer leaves behind yellow where it's not exposed, and the blue forming layer leaves behind orange where it's not exposed. This puts an overall orange bias on the image, and gives the totally unexposed edges of the film that familiar rich orange look. The whole negative / IP / IN / print system is designed around this idea. When you hang neg or IP on a telecine, the orange bias is corrected out.

This orange bias idea was a Kodak invention, shortly after WWII. The Germans had the Agfa negative / positive process, which was clear in the unexposed areas.




-- J.S.
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#18 Chris Millar

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Posted 19 July 2011 - 09:46 PM

The orange mask is not uniform it is inversely proportional to the density of the other layers underneath


oooh, like pyro staining in black and white - but inverse ...
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#19 K Borowski

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Posted 19 July 2011 - 10:43 PM

Inverseely proportional? Orange?

I don't observe teh density of the neg. mask going DOWN when exposed images go up.

And what are we talking about orange for? I read cyan, yellow, magenta dye. I can understand the green layer (magenta) generating yellow dye and blue layer (yellow) generating what magenta, magenta and yellow.

But if we were to see this cancelled out with exposure, wouldn't we run into a point where the density would go DOWN? The average reading for ECN neg in Status M densitometry is something like 20 Cyan ® 65 Magenta (G) 90 Yellow (B) With a gamma of 0.6, that is 4-1/2 stops roughly of yellow that would suddenly disappear with that layer being exposed? Or the other layer or layers being exposed?



Sorry, thought I'd posted this yesterday, must have not clicked the send button.
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#20 Daniel Lee

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Posted 20 July 2011 - 09:33 AM

There is a dMin for the mask. It is additive to density, you cannot decrease something by adding something, it cannot have a negative value for O.D.


This applies to ECN-2 as well;
http://www.apug.org/...range-mask.html

Edited by Daniel Lee, 20 July 2011 - 09:37 AM.

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